Light regulation of metabolic pathways in fungi

Synthesis, characterization, and microbiological evaluation of new triazolopyrimidine-based ferrocenes as potent antimicrobial prospects

Antimicrobial metallodrugs have gained considerable attention for their potent inhibitory activity and clinical success, driving the development of novel metallodrug candidates. These efforts have uncovered new bioactive scaffolds and mechanisms of action. However, the global challenge of antimicrobial resistance (AMR), fueled by the genetic adaptability of microbes and resistance to nearly all antibiotic classes, highlights the urgent need for innovative antibiotics. In this study, we expand the repertoire of metallodrugs by designing, synthesizing, and biologically evaluating triazolopyrimidine-based ferrocenes as antimicrobial agents. These compounds demonstrated broad-spectrum activity against both bacterial and fungal pathogens. Advanced characterization techniques, including NMR, HRMS, FE-SEM, and SCXRD, confirmed their structural integrity and properties. Notably, the ferrocenes exhibited potent antifungal activity against Candida species, comparable to fluconazole, and were effective against Escherichia coli and Staphylococcus aureus. Our findings reveal a new class of metallodrugs with significant antimicrobial potential, offering promising avenues to combat AMR in future.

The effects of different light qualities on the growth and nutritional components of Pleurotus citrinopileatus

Light is one of the key factors affecting the flavor of edible fungi. Pleurotus citrinopileatus were planted in a growth chamber in order to investigate the effects of different LED lights on the growth and development. Five treatments were set up in the experiment, namely white light (CK, as control), pure green light (G), pure blue light (B), pure red light (R) and far-red light (Fr). The results showed that: (1) R or Fr treatment caused deformities in Pleurotus citrinopileatus, showing a soft stipe, thin pileus, and shallow color. Compared with the control, the stipe length of Pleurotus citrinopileatus significantly decreased by 12.52% under treatment B, while the stipe diameter, pileus diameter, and fruiting body weight significantly increased by 35.52%, 18.30%, and 23.66%, respectively (P < 0.05). The color of Pleurotus citrinopileatus was more plump under B treatment, among which the spectral color parameters C and Hue increased by 2.72% and 1.64%, respectively. (2) B increased the proportion of umami and sweet amino acids [(UAA+SAA)/TAA] while decreased that of bitter amino acids in total amino acids (BAA/TAA) in Pleurotus citrinopileatus relative to the control. In addition, except for B treatment, other treatments (G, R, Fr) significantly reduced the content of mushroom flavored amino acids (e.g., Asp and Glu). (3) B increased the odor activity value (OAV) of key aroma compounds in Pleurotus citrinopileatus compared with the other light qualities in this study, while R increased the OAV of 1-octen-3-ol and 1-octen-3-one. However, considering that mushrooms cannot grow normally under R treatment, this study recommended blue light as the main light quality for industrial production of Pleurotus citrinopileatus.

Influence of low-intensity artificial light on the fatty acid profile of the biotechnologically important culinary mushroom Pleurotus eryngii in vitro

BACKGROUND

The problem of searching for environmentally friendly regulators of the biosynthetic activity of edible and medicinal mushrooms is crucial for creating highly effective biotechnologies. One such regulator is light. This study aimed to compare and evaluate the fatty acid profile and fat quality indices of lipids from the mycelial mass of Pleurotus eryngii under various light-emitting diode (LED) and laser light irradiation regimes.

METHODS

To determine the effect of artificial light on the biosynthetic activity of P. eryngii, an artificial lighting system based on LED matrices with wavelengths of 470 nm (blue), 530 nm (green), and 650 nm (red), as well as an argon gas laser as a coherent visible light source at 488 nm, was used. For all experimental variants, the energy density on the surface of the samples was set to the same, providing an energy dose of 240 mJ/cm2. Irradiation was carried continuously.

RESULTS

Twenty-seven fatty acids were identified in the studied P. eryngii mycelial mass samples, including nine saturated fatty acids (SFAs), eight monounsaturated fatty acids (MUFAs) and ten polyunsaturated fatty acids (PUFAs). The control sample (without irradiation) contained the lowest number of fatty acids (fourteen). With irradiation in all modes, a decrease in the amount of SFA and the formation of new MUFA and PUFA with a chain length of C20-C24, which were absent in the control, were observed. Blue light stimulated the synthesis of significant amounts of α-linolenic acid (C18:3ω-3). The ratios of ΣPUFA/ΣSFA, ΣPUFA/ΣMUFA and ΣPUFAω-6/ω-3 in the mass of mycelium irradiated with blue light were within the optimal values for the human diet.

CONCLUSIONS

The selected mycelial photoactivation modes using low-intensity laser and LED light of different spectral composition and coherence may have potential in the biotechnology of submerged cultivation of P. eryngii to obtain mycelial mass with an improved fatty acid profile, which can be considered as a useful source of lipids.

Characterization of Blue Light Receptors LreA and LreB in Aspergillus flavus

Light is a key external signal factor that regulates asexual development, stress resistance, and secondary metabolism in fungi. In the presence of light, photoreceptors sense several light receptors and affect fungal life. In this study, we characterized the function of the blue light receptors LreA and LreB in Aspergillus flavus, a potent pathogenic and toxigenic fungus. lreA or lreB deletion increased the growth rate but decreased conidial production in the presence or absence of light. The ΔlreA-mutant strain and the ΔlreB-mutant strain produced abnormal conidiophores, suggesting that lreA and lreB were essential for proper conidiation in A. flavus. The absence of lreA or lreB slightly decreased the stress response tolerance against thermal and oxidative stresses. In kernel infection, the ΔlreA mutant strain and the ΔlreB mutant strain produced conidia and aflatoxin B1 that were less than those produced by the control strains. Therefore, LreA and LreB play key roles in the growth, asexual development, and pathogenicity of A. flavus.

A Chromosome-Scale Genome of Trametes versicolor and Transcriptome-Based Screening for Light-Induced Genes That Promote Triterpene Biosynthesis

Trametes versicolor is an important fungus with medicinal properties and a significant role in lignocellulose degradation. In this study, we constructed a high-quality chromosome-level genome of T. versicolor using Illumina, PacBio HiFi, and Hi-C sequencing technologies. The assembled genome is 47.42 Mb in size and contains 13,307 protein-coding genes. BUSCO analysis revealed genome and gene completeness results of 95.80% and 95.90%, respectively. Phylogenetic analysis showed that T. versicolor is most closely related to T. pubescens, followed by T. cinnabarina and T. coccinea. Comparative genomic analysis identified 266 syntenic blocks between T. versicolor and Wolfiporia cocos, indicating a conserved evolutionary pattern between the two species. Gene family analysis highlighted the expansion and contraction of genes in functional categories related to the biosynthesis of secondary metabolites, including several T. versicolor-specific genes. Key genes involved in lignocellulose degradation and triterpene production were identified within the CAZyme and CYP450 gene families. Transcriptomic analysis under dark and light conditions revealed significant changes in the expression of genes related to secondary metabolism, suggesting that light signals regulate metabolic pathways. A total of 2577 transporter proteins and 2582 membrane proteins were identified and mapped in the T. versicolor genome, and 33 secondary metabolite gene clusters were identified, including two light-sensitive triterpene biosynthesis clusters. This study offers a comprehensive genomic resource for further investigation into the functional genomics, metabolic regulation, and triterpene biosynthesis of T. versicolor, providing valuable insights into fungal evolution and biotechnological applications.

Characterization of putative antimicrobial compounds produced by endolichenic Fusarium solani exposed to light treatments

The endolichenic Fusarium solani (EF5), known to show induced metabolite production when exposed to red and green lights, was selected for characterization of their putative light-regulated bioactive compounds. To achieve this, fractionation was first performed for crude extracts from cultures of F. solani (EF5) incubated in green, red, white-fluorescent light and dark conditions. The extract yielded 12 (dark condition) to 15 (exposed to green, red, and white-fluorescent lights) fractions, and each of the fractions was tested for antimicrobial activities. The fraction (fraction 5) that showed the most promising antimicrobial activity was then subjected to high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) to identify the bioactive compounds. Results revealed detection of two new metabolites from endolichenic F. solani, putatively identified as 8-deoxyjavanicin and fusolanone A, which are known to have antimicrobial properties. This study revealed that red and green lights trigger the production of 8-deoxyjavanicin and fusolanone A, which likely contributed to the antimicrobial properties demonstrated by endolichenic F. solani.

Yield increment and transcriptome response caused by blue light treatment in Hericium coralloides

BACKGROUND

Hericium coralloides is a traditional edible and medicinal mushroom. Light is a key factor in forming fruiting bodies of fungi; however, the effects of different light on the yield and morphogenesis of H. coralloides are still unknown. Therefore, the morphology, yield, and transcriptome of H. coralloides under blue, red, and white light conditions were investigated.

RESULT

Fruiting bodies under blue light exhibited superior morphological traits, such as milky white color, larger size, elongated stalks, and higher spine count, leading to higher yields. Different light treatments led to dramatic transcriptome changes ranging from 10,827 differentially expressed genes (DEGs) induced by blue light in Blue-4d to 11,375 DEGs induced by red light in Red-4d and accounted for 64.56% to 67.81% of all expressed genes. This massive amount of light-responsive genes has never been reported in fungi. Gene Ontology analysis showed that light affected nearly all aspects of life in H. coralloides; suggesting that the influence of light on fungi may have been underestimated. Blue light-induced yield increment may be achieved by specifically upregulating the growth-related processes such as DNA replication, chromosomes, and cell division.

CONCLUSIONS

This study offers preliminary insights into the potential role of blue light in modulating gene expression and yield stimulation in H. coralloides, potentially improving cultivation practice.

Characterization of Bipolaris bicolor germination: effects of a physical factor on fungal adaptability

Studies on physiological responses to stimuli from physical factors are essential for understanding the dynamics of the microorganisms and higly important for the management of plant diseases. Besides, the development of an epidemiological model for pathogen populations requires studying their physiological responses to physical stimuli. The objective of this study was to evaluate the germination dynamics of spores from six isolates of Bipolaris bicolor under effects of light at 25 °C. Suspensions of 1.6 × 105 conidia mL- 1 from the B. bicolor isolates were inoculated onto Petri dishes containing agar-water culture medium and incubated in a BOD chamber under two physical conditions: (a) constant darkness and (b) constant light for five hours. The study was conducted in a completely randomized design, with a 6 × 2 factorial arrangement (six B. bicolor isolates and two physical conditions) and five replications. The length of the germ tube was measured hourly. The constant darkness resulted in higher mean germ tube growth for the pathogen; however, differences in the final germination percentage were found among the isolates. The isolate F-24-02 exhibited the highest germination adaptability to constant darkness, presenting the longest germ tube length.

Metabolome and transcriptome unveil the mechanism of light on regulating beauvericin synthesis in Cordyceps chanhua

Cordyceps chanhua, an important cordycipitoid medical mushroom with wide use in Asia, has gained attention for its bioactive component beauvericin (BEA), which is of medicinal value as a drug lead, but also of food safety risk. Recent observations by our group revealed a significant decrease of BEA content in C. chanhua when exposed to light, but the underlying regulatory mechanisms remain elusive. In this study, a comprehensive approach combining metabolomics and transcriptomics was employed to investigate the effects of white light on the secondary metabolism of C. chanhua for elucidation of the influence of light on BEA biosynthesis in this fungus. The result showed that the genes and metabolites involved in the synthesis of D-hydroxyisovaleric acid, a precursor of BEA synthesis, were down-regulated under light exposure, while those associated with the synthesis of phenylalanine, another precursor of BEA synthesis, were up-regulated leading to elevated phenylalanine levels. It suggested that the suppressive effect of light on BEA synthesis in C. chanhua occurred primarily through the inhibition of D-hydroxyisovaleric acid synthesis, while the enhanced phenylalanine biosynthesis likely directed towards other metabolic pathway such as pigment synthesis. These results contributed to a better understanding on how light modulates the secondary metabolism of C. chanhua and provided valuable guidance for optimizing BEA production in cultivation practices.

LC-MS/MS-based targeted carotenoid and anthocyanidin metabolic profile of Auricularia cornea under blue and red LED light exposure

Light exposure significantly impacted the coloration and metabolism of Auricularia cornea, although the underlying mechanisms remain unclear. This study aimed to test the apparent color and pigment metabolic profiles of A. cornea in response to red (λp = 630 nm) and blue (λp = 463 nm) visible light exposure. Colorimeter analysis showed that fruiting bodies appeared bright-white under red-light and deeper-red under blue-light, both with a yellow tinge. On the 40th day of light-exposure, bodies were collected for metabolite detection. A total of 481 metabolites were targeted analysis, resulting in 18 carotenoids and 11 anthocyanins. Under red and blue light exposure, the total carotenoids levels were 1.1652 μg/g and 1.1576 μg/g, the total anthocyanins levels were 0.0799 μg/g and 0.1286 μg/g, respectively. Four differential metabolites and three putative gene linked to the visual coloration of A. cornea were identified. This pioneering study provides new insights into the role of light in regulating A. cornea pigmentation and metabolic profile.

Strain heterogeneity in a non-pathogenic Aspergillus fungus highlights factors associated with virulence

Fungal pathogens exhibit extensive strain heterogeneity, including variation in virulence. Whether closely related non-pathogenic species also exhibit strain heterogeneity remains unknown. Here, we comprehensively characterized the pathogenic potentials (i.e., the ability to cause morbidity and mortality) of 16 diverse strains of Aspergillus fischeri, a non-pathogenic close relative of the major pathogen Aspergillus fumigatus. In vitro immune response assays and in vivo virulence assays using a mouse model of pulmonary aspergillosis showed that A. fischeri strains varied widely in their pathogenic potential. Furthermore, pangenome analyses suggest that A. fischeri genomic and phenotypic diversity is even greater. Genomic, transcriptomic, and metabolic profiling identified several pathways and secondary metabolites associated with variation in virulence. Notably, strain virulence was associated with the simultaneous presence of the secondary metabolites hexadehydroastechrome and gliotoxin. We submit that examining the pathogenic potentials of non-pathogenic close relatives is key for understanding the origins of fungal pathogenicity.

Multidimensional discriminant analysis of species, strains and culture age of closely related entomopathogenic fungi using reflectance spectroscopy

The diversity of fungal strains is influenced by genetic and environmental factors, growth conditions and mycelium age, and the spectral features of fungal mycelia are associated with their biochemical, physiological, and structural traits. This study investigates whether intraspecific differences can be detected in two closely related entomopathogenic species, namely Cordyceps farinosa and Cordyceps fumosorosea, using ultraviolet A to shortwave infrared (UVA-SWIR) reflectance spectra. Phylogenetic analysis of all strains revealed a high degree of uniformity among the populations of both species. The characteristics resulting from variation in the species, as well as those resulting from the age of the cultures were determined. We cultured fungi on PDA medium and measured the reflectance of mycelia in the 350-2500 nm range after 10 and 17 days. We subjected the measurements to quadratic discriminant analysis (QDA) to identify the minimum number of bands containing meaningful information. We found that when the age of the fungal culture was known, species represented by a group of different strains could be distinguished with no more than 3-4 wavelengths, compared to 7-8 wavelengths when the age of the culture was unknown. At least 6-8 bands were required to distinguish cultures of a known species among different age groups. Distinguishing all strains within a species was more demanding: at least 10 bands were required for C. fumosorosea and 21 bands for C. farinosa. In conclusion, fungal differentiation using point reflectance spectroscopy gives reliable results when intraspecific and age variations are taken into account.

Safety of the feed additive consisting of endo-1,4-β-xylanase (produced with Trichoderma reesei CBS 143953), subtilisin (produced with Bacillus subtilis CBS 143946) and α-amylase (produced with Bacillus amyloliquefaciens CBS 143954) (Avizyme® 1505) for all poultry species (Danisco (UK) Ltd.)

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety of the feed additive consisting of endo-1,4-β-xylanase (produced with Trichoderma reesei CBS 143953), subtilisin (produced with Bacillus subtilis CBS 143946) and α-amylase (produced with Bacillus amyloliquefaciens CBS 143954) (Avizyme® 1505) as a zootechnical feed additive for all poultry species. The additive is authorised in feed for chickens and turkeys for fattening, ducks and laying hens. In 2020, the FEEDAP Panel issued an opinion for the renewal of the authorisation of the additive for the species/categories for which there is an authorisation, a reduction of the minimum recommended level in turkeys for fattening and the extension of use to all poultry species. In that assessment, the Panel could not conclude on the safety of the additive due to uncertainties on the characterisation of the production strains and the possible presence of their viable cells and DNA in the final product. Moreover, limitations were identified in the xylanase specifications and xylanase method of analysis. The applicant submitted information to address the limitations previously identified. The Panel concluded that the additive is safe for the target species under the proposed conditions of use. The use of Avizyme® 1505 in animal nutrition is considered safe for the consumer and the environment. The additive is a mild irritant to skin and eyes; it is not a dermal sensitiser but should be considered a respiratory sensitiser. The additive is efficacious in ducks at 75 U endo-1,4-β-xylanase, 1000 U subtilisin and 100 U α-amylase/kg of complete feed. In other poultry species for fattening (including turkeys), reared for breeding and reared for laying, the additive is efficacious at 187.5 U endo-1,4-β-xylanase, 2500 U subtilisin and 250 U α-amylase per kg of complete feed and at 300 U endo-1,4-β-xylanase, 4000 U subtilisin and 400 U α-amylase per kg of complete feed for all poultry species for laying (except for ducks).

Different wavelengths of LED irradiation promote secondary metabolite production in Pycnoporus sanguineus for antioxidant and immunomodulatory applications

Pycnoporus sanguineus is a fungus of the phylum Basidiomycota that has many applications in traditional medicine, modern pharmaceuticals, and agricultural industries. Light plays an essential role in the metabolism, growth, and development of fungi. This study evaluated the mycelial growth and antioxidant and anti-inflammatory activities in P. sanguineus fermentation broth (PFB) cultured under different wavelengths of LED irradiation or in the dark. Compared to the dark cultures, the dry weight of mycelia in red- and yellow-light cultures decreased by 37 and 35% and the yields of pigments increased by 30.92 ± 2.18 mg and 31.75 ± 3.06 mg, respectively. Compared with the dark culture, the DPPH free radical scavenging ability, ABTS+ free radical scavenging capacity, and reducing power of yellow-light cultures increased significantly, and their total phenolic content peaked at 180.0 ± 8.34 μg/mL. However, the reducing power in blue-light cultures was significantly reduced, though the total phenol content did not vary with that of dark cultures. In LPS- and IFN-γ-stimulated RAW 264.7 cells, nitrite release was significantly reduced in the red and yellow light-irradiated PFB compared with the dark culture. In the dark, yellow-, and green-light cultures, TNF-α production in the inflamed RAW 264.7 cells was inhibited by 62, 46, and 14%, respectively. With red-, blue-, and white-light irradiation, TNF-α production was significantly enhanced. Based on these results, we propose that by adjusting the wavelength of the light source during culture, one can effectively modulate the growth, development, and metabolism of P. sanguineus.

Red and far-red light improve the antagonistic ability of Trichoderma guizhouense against phytopathogenic fungi by promoting phytochrome-dependent aerial hyphal growth

Light as a source of information regulates morphological and physiological processes of fungi, including development, primary and secondary metabolism, or the circadian rhythm. Light signaling in fungi depends on photoreceptors and downstream components that amplify the signal to govern the expression of an array of genes. Here, we investigated the effects of red and far-red light in the mycoparasite Trichoderma guizhouense on its mycoparasitic potential. We show that the invasion strategy of T. guizhouense depends on the attacked species and that red and far-red light increased aerial hyphal growth and led to faster overgrowth or invasion of the colonies. Molecular experiments and transcriptome analyses revealed that red and far-red light are sensed by phytochrome FPH1 and further transmitted by the downstream MAPK HOG pathway and the bZIP transcription factor ATF1. Overexpression of the red- and far-red light-induced fluffy gene fluG in the dark resulted in abundant aerial hyphae formation and thereby improvement of its antagonistic ability against phytopathogenic fungi. Hence, light-induced fluG expression is important for the mycoparasitic interaction. The increased aggressiveness of fluG-overexpressing strains was phenocopied by four random mutants obtained after UV mutagenesis. Therefore, aerial hyphae formation appears to be a trait for the antagonistic potential of T. guizhouense.

Strain heterogeneity in a non-pathogenic fungus highlights factors contributing to virulence

Fungal pathogens exhibit extensive strain heterogeneity, including variation in virulence. Whether closely related non-pathogenic species also exhibit strain heterogeneity remains unknown. Here, we comprehensively characterized the pathogenic potentials (i.e., the ability to cause morbidity and mortality) of 16 diverse strains of Aspergillus fischeri, a non-pathogenic close relative of the major pathogen Aspergillus fumigatus. In vitro immune response assays and in vivo virulence assays using a mouse model of pulmonary aspergillosis showed that A. fischeri strains varied widely in their pathogenic potential. Furthermore, pangenome analyses suggest that A. fischeri genomic and phenotypic diversity is even greater. Genomic, transcriptomic, and metabolomic profiling identified several pathways and secondary metabolites associated with variation in virulence. Notably, strain virulence was associated with the simultaneous presence of the secondary metabolites hexadehydroastechrome and gliotoxin. We submit that examining the pathogenic potentials of non-pathogenic close relatives is key for understanding the origins of fungal pathogenicity.

Photoregulation of the biosynthetic activity of the edible medicinal mushroom Lentinula edodes in vitro

The findings of the study demonstrate the impact of low-intensity laser and quasi-monochromatic light on the biosynthetic activity of the edible medicinal fungus L. edodes during submerged cultivation. An artificial lighting installation based on matrices of light-emitting diodes (LED) emitting light at 470 nm (blue), 530 nm (green), 650 nm (red), and argon gas laser (488 nm) was used. Irradiation with blue and red LED and laser led to a shortening of the lag phase by 2 days and an increase in the mycelial mass. Irradiation with laser light resulted in the highest mycelial mass yield (14.1 g/L) on the 8th day of cultivation. Irradiation in all used wavelength ranges caused an increase in the synthesis of both extracellular and intracellular polysaccharides. Laser light at 488 nm and LED at 470 nm proved to be the most effective. Irradiation with red, green, and blue laser light caused an increase in the total amount of fatty acids in the mycelial mass compared to the control. A significant distinction in qualitative composition was observed: short-chain acids C6‒C12 compounds were produced under red light irradiation, whereas long-chain C20‒C24 were formed under green light irradiation. The most significant changes in the aromatic profile of the mycelial mass and culture liquid were recorded upon irradiation with green light. The content of aromatic components increased 24.6 times in the mycelial mass and 38.5 times in the culture liquid. The results suggest the possibility of using low-intensity quasi-monochromatic light for targeted regulation of L. edodes biosynthetic activity.

"You Are What You Eat": How Fungal Adaptation Can Be Leveraged toward Myco-Material Properties

Fungi adapt to their surroundings, modifying their behaviors and composition under different conditions like nutrient availability and environmental stress. This perspective examines how a basic understanding of fungal genetics and the different ways that fungi can be influenced by their surroundings can be leveraged toward the production of functional mycelium materials. Simply put, within the constraints of a given genetic script, both the quality and quantity of fungal mycelium are shaped by what they eat and where they grow. These two levers, encompassing their global growth environment, can be turned toward different materials outcomes. The final properties of myco-materials are thus intimately shaped by the conditions of their growth, enabling the design of new biobased and biodegradable material constructions for applications that have traditionally relied on petroleum-based chemicals.This perspective highlights aspects of fungal genetics and environmental adaptation that have potential materials science implications, along the way touching on key studies, both to situate the state of the art within the field and to punctuate the viewpoints of the authors. Finally, this work ends with future perspectives, reinforcing key topics deemed important to consider in emerging myco-materials research.

Characterization of spatio-temporal dynamics of the constrained network of the filamentous fungus Podospora anserina using a geomatics-based approach

In their natural environment, fungi are subjected to a wide variety of environmental stresses which they must cope with by constantly adapting the architecture of their growing network. In this work, our objective was to finely characterize the thallus development of the filamentous fungus Podospora anserina subjected to different constraints that are simple to implement in vitro and that can be considered as relevant environmental stresses, such as a nutrient-poor environment or non-optimal temperatures. At the Petri dish scale, the observations showed that the fungal thallus is differentially affected (thallus diameter, mycelium aspect) according to the stresses but these observations remain qualitative. At the hyphal scale, we showed that the extraction of the usual quantities (i.e. apex, node, length) does not allow to distinguish the different thallus under stress, these quantities being globally affected by the application of a stress in comparison with a thallus having grown under optimal conditions. Thanks to an original geomatics-based approach based on the use of automatized Geographic Information System (GIS) tools, we were able to produce maps and metrics characterizing the growth dynamics of the networks and then to highlight some very different dynamics of network densification according to the applied stresses. The fungal thallus is then considered as a map and we are no longer interested in the quantity of material (hyphae) produced but in the empty spaces between the hyphae, the intra-thallus surfaces. This study contributes to a better understanding of how filamentous fungi adapt the growth and densification of their network to potentially adverse environmental changes.

Comparative Proteomic Analysis Reveals Candidate Pathways Related to the Effect of Different Light Qualities on the Development of Mycelium and Fruiting Body of Pleurotus ostreatus

Light affects the morphology and physiology of Pleurotus ostreatus. However, the underlying molecular mechanism of this effect remains unclear. In this study, a label-free comparative proteomic analysis was conducted to investigate the global protein expression profile of the mycelia and fruiting bodies of P. ostreatus PH11 growing under four different light quality treatments. Among all the 2234 P. ostreatus proteins, 1349 were quantifiable under all tested conditions. A total of 1100 differentially expressed proteins were identified by comparing the light group data with those of the darkness group. GO and KEGG enrichment analyses indicated that the oxidative phosphorylation, proteasome, and mRNA surveillance pathways were the most related pathways under the light condition. qRT-PCR verified that the expression of the white collar 1 protein was significantly enhanced under white light. Additionally, glutamine synthetase and aldehyde dehydrogenase played important roles during light exposure. This study provides valuable insight into the P. ostreatus light response mechanism, which will lay the foundation for improved cultivation.

Nitric oxide mediates red light-induced perylenequinone production in Shiraia mycelium culture

Perylenequinones (PQs) from bambusicolous Shiraia fungi serve as excellent photosensitizers for photodynamic therapy. However, the lower yield of PQ production in mycelium cultures is an important bottleneck for their clinical application. Light has long been recognized as a pivotal regulatory signal for fungal secondary metabolite biosynthesis. In this study, we explored the role of nitric oxide (NO) in the growth and PQ biosynthesis in mycelium cultures of Shiraia sp. S9 exposed to red light. The continuous irradiation with red light (627 nm, 200 lx) suppressed fungal conidiation, promoted hyphal branching, and elicited a notable increase in PQ accumulation. Red light exposure induced NO generation, peaking to 81.7 μmol/g FW on day 8 of the culture, with the involvement of nitric oxide synthase (NOS)- or nitrate reductase (NR)-dependent pathways. The application of a NO donor sodium nitroprusside (SNP) restored conidiation of Shiraia sp. S9 under red light and stimulated PQ production, which was mitigated upon the introduction of NO scavenger carboxy-PTIO or soluble guanylate cyclase inhibitor NS-2028. These results showed that red light-induced NO, as a signaling molecule, was involved in the regulation of growth and PQ production in Shiraia sp. S9 through the NO-cGMP-PKG signaling pathway. While mycelial H2O2 content exhibited no significant alternations, a transient increase of intracellular Ca2+ and extracellular ATP (eATP) content was detected upon exposure to red light. The generation of NO was found to be interdependent on cytosolic Ca2+ and eATP concentration. These signal molecules cooperated synergistically to enhance membrane permeability and elevate the transcript levels of PQ biosynthetic genes in Shiraia sp. S9. Notably, the combined treatment of red light with 5 μM SNP yielded a synergistic effect, resulting in a substantially higher level of hypocrellin A (HA, 254 mg/L), about 3.0-fold over the dark control. Our findings provide valuable insights into the regulation of NO on fungal secondary metabolite biosynthesis and present a promising strategy involving the combined elicitation with SNP for enhanced production of photoactive PQs and other valuable secondary metabolites in fungi.

Growth, morphology, and formation of cinnabarin in Pycnoporus cinnabarinus in relation to different irradiation spectra

BACKGROUND

The demand for natural pigments in general, and for fungi-derived pigments in particular, is constantly rising. Wood-decomposing fungi represent a promising source for natural pigments and they are usually easy to cultivate in pure culture. One of them, i.e., Pycnoporus cinnabarinus, offers a highly interesting spectrum of bioactivity, partly due to the formation of the orange-red pigment cinnabarin. However, apart from a few studies addressing its diverse potential biotechnological applications, there is still a large gap of knowledge concerning the influence of light on the formation of cinnabarin. The aim of this work was to investigate the effect of different irradiations on the cinnabarin content, the growth, and the morphology of three different P. cinnabarinus strains. We used highly standardized irradiation conditions and cultivation techniques in combination with newly developed methods for the extraction and direct quantification of cinnabarin.

RESULTS

Red, green, blue, and UV-A irradiation (mean irradiance Ee = 1.5 ± 0.18 W m-2) had considerable effects on the growth and colony appearance of all three P. cinnabarinus strains tested. The cinnabarin content determined was, thus, dependent on the irradiation wavelength applied, allowing strain-specific thresholds to be defined. Irradiation with wavelengths below this strain-specific threshold corresponded to a lower cinnabarin content, at least at the intensity applied. The orange-red pigment appeared by light microscopy as incrusted extracellular plaques present on the hyphal walls. Highly efficient vegetative propagation occurred by arthroconidia, and we observed the tendency that this asexual reproduction was (i) most frequent in the dark but (ii) never occurred under UV-A exposure.

CONCLUSION

 This study highlights a differential photo-dependence of growth, morphology, and cinnabarin formation in P. cinnabarinus. This confirms that it is advisable to consider the wavelength of the light used in future biotechnological productions of natural pigments.

Identification and evaluation of suitable reference genes for RT-qPCR analyses in Trichoderma atroviride under varying light conditions

BACKGROUND

Trichoderma atroviride is a competitive soil-borne mycoparasitic fungus with extensive applications as a biocontrol agent in plant protection. Despite its importance and application potential, reference genes for RT-qPCR analysis in T. atroviride have not been evaluated. Light exerts profound effects on physiology, such as growth, conidiation, secondary metabolism, and stress response in T. atroviride, as well as in other fungi. In this study, we aimed to address this gap by identifying stable reference genes for RT-qPCR experiments in T. atroviride under different light conditions, thereby enhancing accurate and reliable gene expression analysis in this model mycoparasite. We measured and compared candidate reference genes using commonly applied statistical algorithms.

RESULTS

Under cyclic light-dark cultivation conditions, tbp and rho were identified as the most stably expressed genes, while act1, fis1, btl, and sar1 were found to be the least stable. Similar stability rankings were obtained for cultures grown under complete darkness, with tef1 and vma1 emerging as the most stable genes and act1, rho, fis1, and btl as the least stable genes. Combining the data from both cultivation conditions, gapdh and vma1 were identified as the most stable reference genes, while sar1 and fis1 were the least stable. The selection of different reference genes had a significant impact on the calculation of relative gene expression, as demonstrated by the expression patterns of target genes pks4 and lox1.

CONCLUSION

The data emphasize the importance of validating reference genes for different cultivation conditions in fungi to ensure accurate interpretation of gene expression data.

Light regulation of secondary metabolism in fungi

Fungi have evolved unique metabolic regulation mechanisms for adapting to the changing environments. One of the key features of fungal adaptation is the production of secondary metabolites (SMs), which are essential for survival and beneficial to the organism. Many of these SMs are produced in response to the environmental cues, such as light. In all fungal species studied, the Velvet complex transcription factor VeA is a central player of the light regulatory network. In addition to growth and development, the intensity and wavelength of light affects the formation of a broad range of secondary metabolites. Recent studies, mainly on species of the genus Aspergillus, revealed that the dimer of VeA-VelB and LaeA does not only regulate gene expression in response to light, but can also be involved in regulating production of SMs. Furthermore, the complexes have a wide regulatory effect on different types of secondary metabolites. In this review, we discussed the role of light in the regulation of fungal secondary metabolism. In addition, we reviewed the photoreceptors, transcription factors, and signaling pathways that are involved in light-dependent regulation of secondary metabolism. The effects of transcription factors on the production of secondary metabolites, as well as the potential applications of light regulation for the production of pharmaceuticals and other products were discussed. Finally, we provided an overview of the current research in this field and suggested potential areas for future research.

Inducing antioxidant and antimicrobial activities in endophytic and endolichenic fungi by the use of light spectra treatments

The influence of light exposure on antioxidant and antimicrobial activities of nine fungal isolates [Pseudopestalotiopsis theae (EF13), Fusarium solani (EF5), Xylaria venustula (PH22), Fusarium proliferatum (CCH), Colletotrichum boninese (PL9), Colletotrichum boninese (PL1), Colletotrichum boninese (OL2), Colletotrichum gloeosporioides (OL3) and Colletotrichum siamense (PL3)] were determined. The isolates were incubated in blue, red, green, yellow and white fluorescent light (12 h photoperiod of alternating light/dark). It was observed that green light induced higher total phenolic content (TPC) (2.96 ± 0.16 mg-30.71 ± 1.03 mg GAE/g) and ferric reducing antioxidant power (FRAP) in most isolates (4.82 ± 0.04-53.55 ± 4.33 mg GAE/g), whereas red light induced higher total flavonoid content (TFC) levels (1.14 ± 0.08-18.40 ± 1.12 mg QE/g). The crude extracts from most fungal cultures exposed to green and red lights were also notably more potent against the tested pathogens, as larger zones of inhibition (ZOI) (9.00 ± 1.00-38.30 ± 2.90 mm) and lower minimum inhibitory concentration (MIC) (0.0196-1.25 mg/mL) were achieved for antimicrobial effect. This study showed that light treatments are effective strategies in enhancing production of more potent antimicrobial compounds and valuable antioxidants from fungal isolates.

Light in the box-photobiological examination chamber with light trap ventilation system for studying fungal surface cultures illustrated with Metarhizium brunneum and Beauveria brongniartii

Due to their versatile way of life as saprophytes, endophytes, and entomopathogens, fungi of the genera Metarhizium and Beauveria are exposed to varying illumination conditions in their natural habitats, which makes a thorough adaptation to light very likely. While the few available studies for these genera support this assumption, research in this field is still in its infancy and the data material restricted to only a few fungal species. Thus, the aim of this work was to explore how light influences growth, conidial production and secondary metabolite formation of two industrial relevant strains of M. brunneum (MA 43, formerly M. anisopliae var. anisopliae BIPESCO 5/F52) and B. brongniartii (BIPESCO 2). To achieve this, we constructed an easily adjustable illumination device for highly standardized photophysiological studies of fungi on Petri dishes, the so-called LIGHT BOX. With the aid of this device, M. brunneum and B. brongniartii were grown on S4G or S2G agar at 25 °C for 14 days either in complete darkness or under constant illumination with red light (λpeak = 635 nm), green light (λpeak = 519 nm) or blue light (λpeak = 452 nm). In addition, for each wavelength the effect of different illumination intensities was tested, i.e., intensities of red light ranging from 22.1 ± 0.1 to 136.5 ± 0.3 µW cm-2, green light from 16.5 ± 0.1 to 96.2 ± 0.1 µW cm-2, and blue light from 56.1 ± 0.2 to 188.9 ± 0.6 µW cm-2. Both fungi strongly responded in terms of growth, conidial production, pigmentation and morphology to changes in the wavelength and irradiation intensity. The wavelength-dependent production of the well-known secondary metabolite oosporein which is secreted by the genus Beauveria in particular, was also increased under green and blue light exposure. The established LIGHT BOX system allows not only to optimize conidial production yields with these biotechnologically relevant fungi, but also allows the photobiological exploration of other fungi.

Exploration of the Production of Three Thiodiketopiperazines by an Endophytic Fungal Strain of Cophinforma mamane

Endophytic fungi possess a versatile metabolism which is related to their ability to live in diverse ecological niches. While culturing under laboratory conditions, their metabolism is mainly influenced by the culture media, time of incubation and other physicochemical factors. In this study, we focused on the production of 3 thiodiketopiperazines (TDKPs) botryosulfuranols A-C produced by an endophytic strain of Cophinforma mamane isolated from the leaves of Bixa orellana L collected in the Peruvian Amazon. We studied the time-course production of botryosulfuranols A-C during 28 days and evaluated the variations in the production of secondary metabolites, including the TDKPs, produced by C. mamane in response to different culture media, light versus dark conditions and different incubation times. We observed a short time-frame production of botryosulfuranol C while its production was significantly affected by the light conditions and nutrients of the culture media. Botryosulfuranols A and B showed a similar production pattern and a similar response to culturing conditions. Molecular networking allowed us to detect three compounds related to TDKPs that will be the focus of future experiments.

NPAS2 promotes aerobic glycolysis and tumor growth in prostate cancer through HIF-1A signaling

BACKGROUND

Prostate cancer (PCa), one of the common malignant tumors, is the second leading cause of cancer-related deaths in men. The circadian rhythm plays a critical role in disease. Circadian disturbances are often found in patients with tumors and enable to promote tumor development and accelerate its progression. Accumulating evidence suggests that the core clock gene NPAS2 (neuronal PAS domain-containing protein 2) has been implicated in tumors initiation and progression. However, there are few studies on the association between NPAS2 and prostate cancer. The purpose of this paper is to investigate the impact of NPAS2 on cell growth and glucose metabolism in prostate cancer.

METHODS

Quantitative real-time PCR (qRT-PCR), immunohistochemical (IHC) staining, western blot, GEO (Gene Expression Omnibus) and CCLE (Cancer Cell Line Encyclopedia) databases were used to analyze the expression of NPAS2 in human PCa tissues and various PCa cell lines. Cell proliferation was assessed using MTS, clonogenic assays, apoptotic analyses, and subcutaneous tumor formation experiments in nude mice. Glucose uptake, lactate production, cellular oxygen consumption rate and medium pH were measured to examine the effect of NPAS2 on glucose metabolism. The relation of NPAS2 and glycolytic genes was analyzed based on TCGA (The Cancer Genome Atlas) database.

RESULTS

Our data showed that NPAS2 expression in prostate cancer patient tissue was elevated compared with that in normal prostate tissue. NPAS2 knockdown inhibited cell proliferation and promoted cell apoptosis in vitro and suppressed tumor growth in a nude mouse model in vivo. NPAS2 knockdown led to glucose uptake and lactate production diminished, oxygen consumption rate and pH elevated. NPAS2 increased HIF-1A (hypoxia-inducible factor-1A) expression, leading to enhanced glycolytic metabolism. There was a positive correlation with the expression of NPAS2 and glycolytic genes, these genes were upregulated with overexpression of NPAS2 while knockdown of NPAS2 led to a lower level.

CONCLUSION

NPAS2 is upregulated in prostate cancer and promotes cell survival by promoting glycolysis and inhibiting oxidative phosphorylation in PCa cells.

Identification, Pathogenicity, and Culture Conditions of a New Isolate of Cordyceps javanica (Hypocreales: Cordycipitaceae) From Soil

This study decribes a highly effective insecticidal isolate of Cordyceps javanica (Frieder. & Bally) (Hypocreales: Cordycipitaceae) named IJ-tg19, which was isolated from soil. Spray bioassays were performed with IJ-tg19 on Myzus persicae (Sulzer) (Hemiptera: Aphididae) adults, third-instar nymphs of Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae), and third-instar larvae of Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) to determine the pathogenicity of the isolate. The corrected mortality rates for all three pests were 100% when the conidia concentration was 1 × 106 conidia/ml, the lowest concentration in this study, and the median survival times (MST) were 4, 4, and 3 d. The MST shortens with increasing conidia concentration. The effects of laboratory culture conditions on the sporulation and growth of the isolate were also studied. This isolate had the greatest conidia production and fastest growth rate on malt extract agar medium at 25°C. The amount of conidia produced had positive correlation to light duration, with the highest production at 24 hr light. The growth of mycelium can adapt to a moderately alkaline environment, but the optimum conidial production occurred at the pH of 7. Our finding and research will be useful in biocontrol programs that are considering using the new isolate of C. javanica against greenhouse pests.

Strategies for Controlling the Sporulation in Fusarium spp

Fusarium species are the most destructive phytopathogenic and toxin-producing fungi, causing serious diseases in almost all economically important plants. Sporulation is an essential part of the life cycle of Fusarium. Fusarium most frequently produces three different types of asexual spores, i.e., macroconidia, chlamydospores, and microconidia. It also produces meiotic spores, but fewer than 20% of Fusaria have a known sexual cycle. Therefore, the asexual spores of the Fusarium species play an important role in their propagation and infection. This review places special emphasis on current developments in artificial anti-sporulation techniques as well as features of Fusarium's asexual sporulation regulation, such as temperature, light, pH, host tissue, and nutrients. This description of sporulation regulation aspects and artificial anti-sporulation strategies will help to shed light on the ways to effectively control Fusarium diseases by inhibiting the production of spores, which eventually improves the production of food plants.

Effect of Different Light Qualities and Intensities on the Yield and Quality of Facility-Grown Pleurotus eryngii

Proper light is essential for the formation and development of macrofungi fruiting bodies. Currently, there are unclear treatment conditions, such as light quality and light intensity, in the production of Pleurotus eryngii in intensive cultivation facilities, which is not helpful to the formation and implementation of standardized production programs. The research discussed in this paper investigated the effects of different light quality and intensity conditions on the yield and quality of P. eryngii. The results showed that the yield and nutritional quality of the red light treatment samples were higher than those of the white light control, the commercial properties were good, and the energy consumption of the red LED light source was the lowest under the same light intensity. The results of this experiment further provide a reference for the energy-saving and high-quality cultivation of P. eryngii.

Light conditions affect the growth, chemical composition, antioxidant and antimicrobial activities of the white-rot fungus Lentinus crinitus mycelial biomass

The mycelial biomass of basidiomycetes is a promising source of compounds and represents an alternative for industrial and biotechnological applications. Fungi use light as information and hold photoresponse mechanisms, in which sensors respond to light wavelengths and regulate various biological processes. Therefore, this study aimed to investigate the effects of blue, green, and red lights on the growth, chemical composition, and antioxidant and antimicrobial activity of Lentinus crinitus mycelial biomass. The chemical composition of the mycelial biomass was determined by chromatographic methods, antioxidant activity was analyzed by in vitro assays, and antimicrobial activity was investigated by the microdilution assay. The highest mycelial biomass yield was observed under blue-light cultivation. Many primordia arose under blue or green light, whereas the stroma was formed under red light. The presence of light altered the primary fungal metabolism, increasing the carbohydrate, tocopherol, fatty acid, and soluble sugar contents, mostly mannitol, and reducing the protein and organic acid concentrations. Cultivation under red light increased the phenol concentration. In contrast, cultivation under blue and green lights decreased phenol concentration. Benzoic and gallic acids were the main phenolic acids in the hydroalcoholic extracts, and the latter acids increased in all cultures under light, especially red light. Mycelial biomass cultivated under red light showed the highest antioxidant activity in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The ferric reducing antioxidant power (FRAP) method showed that all light wavelengths increased the antioxidant activity of mycelial biomass, with the highest value under red light. Moreover, the β-carotene/linoleic acid co-oxidation (BCLA) assay demonstrated that the antioxidant activity was affected by light cultivation. Mycelial biomass grown under all conditions exhibited antibacterial and antifungal activities. Thus, mycelial biomass cultivation of L. crinitus under light conditions may be a promising strategy for controlling the mycelial chemical composition and biomass yield.

Assessment of the feed additive consisting of endo-1,4-β-xylanase produced by Trichoderma reesei CBS 143953 and endo-1,3(4)-β-glucanase produced by T. reesei CBS 143945 (Axtra® XB 201 TPT/L) for poultry and pigs for renewal of its authorisation (Danisco (UK) Ltd)

Following a request from the European Commission, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the renewal of the authorisation of endo-1,4-β-xylanase produced by Trichoderma reesei CBS 143953 and endo-1,3(4)-β-glucanase produced by T. reesei CBS 143945 (Axtra® XB 201 TPT/L) as a zootechnical feed additive (digestibility enhancers) for poultry and pigs. The endo-1,4-β-xylanase and endo-1,3(4)-β-glucanase are produced by a genetically modified strain of T. reesei and a non-genetically modified strain of T. reesei, respectively. The applicant also requested a reduction of the minimum recommended level for turkeys for fattening and the extension of use to other species/categories. The Panel concluded that the additive complies with the conditions of the current authorisation. There is no new evidence that would lead the FEEDAP Panel to reconsider previous conclusions on the safety of the additive. These conclusions apply also to the new target species/categories for which a request of use was made, suckling piglets. The Panel concluded that the additive should be considered irritant to eyes and a respiratory sensitiser. However, no conclusions could be drawn on the skin irritancy/sensitisation potential of the additive. No change in the authorisation conditions were requested for poultry species (other than turkeys), weaned piglets, pigs for fattening, sows and minor porcine species; therefore there was no need for an assessment on the efficacy of the additive for those species/categories. The Panel concluded that the additive has the potential to be efficacious in turkeys for fattening/reared for breeding and in suckling piglets (for the period in which solid feed is administered) at an intended level of 610 xylanase U/kg and 76 glucanase U/kg feed. However, the Panel noted that the actual effective level used in the studies supporting this conclusion was approximately 50% higher than the intended level.

Safety and efficacy of a feed additive consisting of 6-phytase produced by Trichoderma reesei CBS 146250 (Axtra® PHY GOLD 30L, Axtra® PHY GOLD 30T, Axtra® PHY GOLD 65G) for all poultry species and all pigs (Danisco (UK) ltd)

Following a request from the European Commission, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety and efficacy of 6-phytase produced by the genetically modified strain Trichoderma reesei CBS 146250 (Axtra® PHY GOLD 30L, Axtra® PHY GOLD 30 T and Axtra® PHY GOLD 65G) as a zootechnical feed additive for all poultry species and all pigs. The FEEDAP Panel concluded that the genetic modification of the production strain does not give rise to safety concerns. Based on the no observed adverse effect level identified in a subchronic oral toxicity study in rats, the additive was considered safe for all poultry species and all pigs at the proposed conditions of use. The Panel also concluded that the use of the product as a feed additive does not give rise to concerns for consumers and the environment. Owing to the lack of data obtained with the final formulations, the Panel cannot conclude on the potential of the additive to be irritant to eyes or skin. Due to the proteinaceous nature of the active substance, it is considered a respiratory sensitiser. The panel concludes that the additive is efficacious in increasing the phosphorus utilisation when supplemented at 500 FTU/kg for all growing poultry species and all pigs, and at 300 FTU/kg in laying hens and other laying birds.

Blue Light-Dependent Pre-mRNA Splicing Controls Pigment Biosynthesis in the Mushroom Terana caerulea

Light induces the production of ink-blue pentacyclic natural products, the corticin pigments, in the cobalt crust mushroom Terana caerulea. Here, we describe the genetic locus for corticin biosynthesis and provide evidence for a light-dependent dual transcriptional/cotranscriptional regulatory mechanism. Light selectively induces the expression of the corA gene encoding the gateway enzyme, the first described mushroom polyporic acid synthetase CorA, while other biosynthetic genes for modifying enzymes necessary to complete corticin assembly are induced only at lower levels. The strongest corA induction was observed following exposure to blue and UV light. A second layer of regulation is provided by the light-dependent splicing of the three introns in the pre-mRNA of corA. Our results provide insight into the fundamental organization of how mushrooms regulate natural product biosynthesis. IMPORTANCE The regulation of natural product biosyntheses in mushrooms in response to environmental cues is poorly understood. We addressed this knowledge gap and chose the cobalt crust mushroom Terana caerulea as our model. Our work discovered a dual-level regulatory mechanism that connects light as an abiotic stimulus with a physiological response, i.e., the production of dark-blue pigments. Exposure to blue light elicits strongly increased transcription of the gene encoding the gateway enzyme, the polyporic acid synthetase CorA, that catalyzes the formation of the pigment core structure. Additionally, light is a prerequisite for the full splicing of corA pre-mRNA and, thus, its proper maturation. Dual transcriptional/cotranscriptional light-dependent control of fungal natural product biosynthesis has previously been unknown. As it allows the tight control of a key metabolic step, it may be a much more prevalent mechanism among these organisms.

De Novo Assembly Transcriptome Analysis Reveals the Preliminary Molecular Mechanism of Primordium Formation in Pleurotus tuoliensis

Primordium formation is extremely important for yield of Pleurotus tuoliensis. However, the molecular mechanism underlying primordium formation is largely unknown. This study investigated the transcriptional properties during primordium formation of P. tuoliensis by comparing transcriptome. Clean reads were assembled into 57,075 transcripts and 6874 unigenes. A total of 1397 differentially expressed genes were identified (26 DEGs altered in all stages). GO and KEGG enrichment analysis showed that these DEGs were involved in “oxidoreductase activity”, “glycolysis/gluconeogenesis”, “MAPK signaling pathways”, and “ribosomes”. Our results support further understanding of the transcriptional changes and molecular processes underlying primordium formation and differentiation of P. tuoliensis.

Circadian oscillations in Trichoderma atroviride and the role of core clock components in secondary metabolism, development, and mycoparasitism against the phytopathogen Botrytis cinerea

Circadian clocks are important for an individual’s fitness, and recent studies have underlined their role in the outcome of biological interactions. However, the relevance of circadian clocks in fungal–fungal interactions remains largely unexplored. We sought to characterize a functional clock in the biocontrol agent Trichoderma atroviride to assess its importance in the mycoparasitic interaction against the phytopathogen Botrytis cinerea. Thus, we confirmed the existence of circadian rhythms in T. atroviride, which are temperature-compensated and modulated by environmental cues such as light and temperature. Nevertheless, the presence of such molecular rhythms appears to be highly dependent on the nutritional composition of the media. Complementation of a clock null (Δfrq) Neurospora crassa strain with the T. atroviride-negative clock component (tafrq) restored core clock function, with the same period observed in the latter fungus, confirming the role of tafrq as a bona fide core clock component. Confrontation assays between wild-type and clock mutant strains of T. atroviride and B. cinerea, in constant light or darkness, revealed an inhibitory effect of light on T. atroviride’s mycoparasitic capabilities. Interestingly, when confrontation assays were performed under light/dark cycles, T. atroviride’s overgrowth capacity was enhanced when inoculations were at dawn compared to dusk. Deleting the core clock-negative element FRQ in B. cinerea, but not in T. atroviride, was vital for the daily differential phenotype, suggesting that the B. cinerea clock has a more significant influence on the result of this interaction. Additionally, we observed that T. atroviride clock components largely modulate development and secondary metabolism in this fungus, including the rhythmic production of distinct volatile organic compounds (VOCs). Thus, this study provides evidence on how clock components impact diverse aspects of T. atroviride lifestyle and how daily changes modulate fungal interactions and dynamics.

Tools for adapting to a complex habitat: G-protein coupled receptors in Trichoderma

Sensing the environment and interpretation of the received signals are crucial competences of living organisms in order to properly adapt to their habitat, succeed in competition and to reproduce. G-protein coupled receptors (GPCRs) are members of a large family of sensors for extracellular signals and represent the starting point of complex signaling cascades regulating a plethora of intracellular physiological processes and output pathways in fungi. In Trichoderma spp. current research involves a wide range of topics from enzyme production, light response and secondary metabolism to sexual and asexual development as well as biocontrol, all of which require delicate balancing of resources in response to the environmental challenges or biotechnological needs at hand, which are crucially impacted by the surroundings of the fungi and their intercellular signaling cascades triggering a precisely tailored response. In this review we summarize recent findings on sensing by GPCRs in Trichoderma, including the function of pheromone receptors, glucose sensing by CSG1 and CSG2, regulation of secondary metabolism by GPR8 and impacts on mycoparasitism by GPR1. Additionally, we provide an overview on structural determinants, posttranslational modifications and interactions for regulation, activation and signal termination of GPCRs in order to inspire future in depth analyses of their function and to understand previous regulatory outcomes of natural and biotechnological processes modulated or enabled by GPCRs.

Light driven Aspergillus niger-ZnS nanobiohybrids for degradation of methyl orange

Inorganic-microbial hybrid systems have potential to be sustainable, efficient and versatile chemical synthesis platforms by integrating the light-harvesting properties of semiconductors with microbial cells. Here, we demonstrate light-driven photocatalytic semiconducting Aspergillus niger cells-ZnS nanoparticles for enhanced removal of the dye methyl orange. Chemically synthesized ZnS nanoparticles exhibited a zinc blende pattern in X-ray diffraction, had a dimension of 20-90 nm with a band gap (E_bg) of 3.4 eV at 1.83 × 10¹⁸ photons/second. Biologically synthesized ZnS nanoparticles of 40-90 nm showed a hexagonal pattern in the X-ray powder diffraction spectra with an E_bg 3.7 eV at 1.68 × 10¹⁸ photons/second. At a methyl orange (MO) concentration of 100 mg/L, dosage of 0.5 × 10⁵ mol catalyst and pH 4, a 97.5% and 98% removal efficiency of MO was achieved in 90 min and 60 min for, respectively, chemically and biologically synthesized ZnS nanobiohybrids in the presence of UV-A light. The major degradation products of photocatalysis for chemically synthesized ZnS nanobiohybrids were naphtholate (C₁₀H₇O m/z 143) and hydroquinone (C₉H₅m/z 113). For the biologically synthesized ZnS nanobiohybrids, the degradation products were hydroquinone (C₉H₅m/z 113) and 2-phenylphenol (C₁₂H₁₀O m/z 170).

The effect of indoor daylight spectrum and intensity on viability of indoor pathogens on different surface materials

Built environments play a key role in the transmission of infectious diseases. Ventilation rates, air temperature, and humidity affect airborne transmission while cleaning protocols, material properties and light exposure can influence viability of pathogens on surfaces. We investigated how indoor daylight intensity and spectrum through electrochromic (EC) windows can impact the growth rate and viability of indoor pathogens on different surface materials (polyvinyl chloride [PVC] fabric, polystyrene, and glass) compared to traditional blinds. Results showed that tinted EC windows let in higher energy, shorter wavelength daylight than those with clear window and blind. The growth rates of pathogenic bacteria and fungi were significantly lower in spaces with EC windows compared to blinds: nearly 100% growth rate reduction was observed when EC windows were in their clear state followed by 41%-100% reduction in bacterial growth rate and 26%-42% reduction in fungal growth rate when EC windows were in their darkest tint. Moreover, bacterial viabilities were significantly lower on PVC fabric when they were exposed to indoor light at EC-tinted window. These findings are deemed fundamental to the design of healthy modern buildings, especially those that encompass sick and vulnerable individuals.

Involvement of VIVID in white light-responsive pigmentation, sexual development and sterigmatocystin biosynthesis in the filamentous fungus Podospora anserina

Light serves as a source of information and regulates diverse physiological processes in living organisms. Fungi perceive and respond to light through a complex photosensory system. Fungi have evolved the desensitization mechanism to adapt to the changing light signal in a natural environment. White light exerts multiple essential impacts on the model filamentous fungus P. anserina. However, the light sensing and response in this species has not been investigated. In this study, we demonstrated that the loss of function of the light desensitization protein VIVID (VVD) in P. anserina triggered exacerbated light responses, and therefore led to drastic morphological and physiological changes. The white light-sensitive mutant Δvvd showed growth reduction, spermatia overproduction, enhanced hyphae pigmentation and reduced oxidative stress tolerance. We observed the decreased expression level of sterigmatocystin gene cluster by transcriptome analysis, and finally detected the reduced production of sterigmatocystin in Δvvd in response to white light. Our data indicate that VVD acts as a repressor of white collar complex. This study exhibits a vital role of VVD in governing white light-responsive gene expression and secondary metabolite production, and contributes to a better understanding of the photoreceptor VVD in P. anserina. This article is protected by copyright. All rights reserved.

Factors regulating cellulolytic gene expression in filamentous fungi: an overview

The growing demand for biofuels such as bioethanol has led to the need for identifying alternative feedstock instead of conventional substrates like molasses, etc. Lignocellulosic biomass is a relatively inexpensive feedstock that is available in abundance, however, its conversion to bioethanol involves a multistep process with different unit operations such as size reduction, pretreatment, saccharification, fermentation, distillation, etc. The saccharification or enzymatic hydrolysis of cellulose to glucose involves a complex family of enzymes called cellulases that are usually fungal in origin. Cellulose hydrolysis requires the synergistic action of several classes of enzymes, and achieving the optimum secretion of these simultaneously remains a challenge. The expression of fungal cellulases is controlled by an intricate network of transcription factors and sugar transporters. Several genetic engineering efforts have been undertaken to modulate the expression of cellulolytic genes, as well as their regulators. This review, therefore, focuses on the molecular mechanism of action of these transcription factors and their effect on the expression of cellulases and hemicellulases.

Influence of substrate wood species on the formation of antiviral properties of <I>Inonotus rheades</I> Pers. P. Karst. (1882) mycelium extracts regarding tick-borne encephalitis virus

Background. The tick-borne encephalitis virus (TBEV) is one of the most dangerous and epidemiologically significant vector-borne pathogens. There is a need for effective antiviral agents for the treatment and prevention of this infection. Previously we found that the mycelium of Inonotus rheades grown on birch wood contains water-soluble substances with strong virulicidal properties against TBEV. It is necessary to check whether the mycelium of I. rheades can synthesize virulicidal substances from wood of other species.

The aim: to study the antiviral properties of extracts of I. rheades mycelium grown on coniferous wood, both in the presence and in the absence of blue light during cultivation.

Materials and methods. The mycelium of I.  rheades was grown on birch, pine, and fir wood. The direct virulicidal effect of the extract was evaluated by the decrease in the titer of the infectious virus incubated in the presence of the extract. The ability of the extract to inhibit the reproduction of the virus in infected cells was studied by  the  calculation of 50  % effective concentration (EC50). The toxicity of extracts for cells was evaluated based on the calculation of 50 % cytotoxic concentration.

Results. Mycelium extracts grown on conifers under blue light do not cause a statistically significant decrease in the concentration of infectious TBEV (p = 0.2563). However, the BP10 extract (pine, blue light) inhibits TBEV reproduction in infected cells (EC50 = 0.28 ± 0.06 mg/mL). Toxicity for SPEV cell culture is low. In the extracts of conifers grown in the dark, no antiviral effect was found at all.

Conclusions. The component composition and mechanism of the antiviral action of I. rheades extracts are determined by the species of the wood substrate. The most promising sources of new drugs in relation to TBEV appear to be extracts of I. rheades mycelium grown on birch and pine. 

Bacterial Community Composition in the Growth Process of Pleurotus eryngii and Growth-Promoting Abilities of Isolated Bacteria

The effects of biological factors on the vegetative growth process of mushrooms remain largely unexplored. We investigated the bacterial community in different growth stages of Pleurotus eryngii by high-throughput sequencing technology to explore the relationship between interacting bacteria and the growth and development of P. eryngii. We found significant variances in mushroom interacting association bacteria (MIAB) compositions among the samples from different growth stages, and 410 genera were identified. The bacteria in the full-bag and post-ripe stages were shifted to the biocontrol and growth-promotion ones. The mushroom growth-promoting bacteria (MGPB) were also isolated successfully and identified as B. cereus Bac1. The growth speed and density of mycelial pellets of P. eryngii, and activities of two exoenzymes (laccase and amylase), were analyzed by adding the different volumes of cell-free fermentation broth of B. cereus Bac1 to fungal culture media. The results showed that when a 5 mL cell-free fermentation broth was used, the growth speed of P. eryngii hyphae was enhanced by 1.15-fold over the control and reached 0.46 mm/h. The relative activity of laccase and amylase was increased by 26.9 and 43.83%. Our study revealed that the abundant interacting bacteria coexist with P. eryngii hyphae. Moreover, the abundance of some bacteria exhibiting a positive correlation with the growth periods of their host fungi can effectively promote the growth of the host, which will provide technical supports on the high-efficiency production of P. eryngii in factory cultivation.

Roles of AaVeA on Mycotoxin Production via Light in Alternaria alternata

Alternaria alternata is a principal plant pathogen responsible for the biosynthesis of mycotoxins, including tenuazonic acid (TeA), alternariol (AOH), and alternariol monomethyl ether (AME). The velvet gene VeA is involved in fungal growth, development, and secondary metabolism, including mycotoxin biosynthesis via light regulation. In this study, the detailed regulatory roles of AaVeA in A. alternata with various light sources were investigated from the comparative analyses between the wild type and the gene knockout strains. In fungal growth and conidiation, mycelial extension was independent of light regulation in A. alternata. Red light favored conidiation, but blue light repressed it. The absence of AaVeA caused the marked reduction of hyphae extension and conidiophore formation even though red light could not induce more spores in ΔAaVeA mutant. The differentially expressed genes (DEGs) enriched in hyphal growth and conidiation were drastically transcribed from the comparatively transcriptomic profile between the wild type and ΔAaVeA mutant strains with or without light. In mycotoxin production, TeA biosynthesis seems no obvious effect by light regulation, but AOH and AME formation was significantly stimulated by blue light. Nevertheless, the disruption of AaVeA resulted in a marked decrease in mycotoxin production and the action of the stimulation was lost via blue light for the abundant accumulation of AOH and AME in the ΔAaVeA strain. From DEG expression and further verification by RT-qPCR, the loss of AaVeA caused the discontinuous supply of the substrates for mycotoxin biosynthesis and the drastic decline of biosynthetic gene expression. In addition, pathogenicity depends on AaVeA regulation in tomato infected by A. alternata in vivo. These findings provide a distinct understanding of the roles of AaVeA in fungal growth, development, mycotoxin biosynthesis, and pathogenicity in response to various light sources.